This invention relates to grounding devices and more particularly to an automatic high voltage grounding device to short high voltages within a cabinet to cabinet ground when a cabinet access door is opened.
During the design of a high power transmitter, it was recognized that a positive, highly visible, failsafe method of shorting the lethal high voltages within the cabinet to cabinet ground was required whenever the cabinet access door was opened, for the safety of maintenance personnel.
All known grounding devices to accomplish these requirements make use of a spring loaded push rod which actuates a mechanism that engages the high voltage contacts when the cabinet door is opened. By its nature, a push rod is a linear motion device which requires guides or bushings for alignment and is susceptible to binding. This problem of binding is further aggravated by the fact that the portion of the access door operating on the actuating rod is not along the axis of the rod, but includes some force perpendicular to its axis.
The spring force to actuate the rod has its shortcomings also. Contact pressure is directly proportional to spring compressive force and is minimum when the access door is open (contacts shorted). Conversely, spring compressive force increases as the access door is closed which requires locating the device near a door latch or a relatively stiff section of the access door to ensure that the mechanism is fully disengaged from the high voltage contacts when the access door is closed.
In applications where the requirements of a positive, highly visible, failsafe method of shorting the lethal high voltages to ground are critical to the safety of maintenance personnel, the above-mentioned grounding technique is unacceptable.